The possible effect of stratospheric quasi-biennial oscillation on the critical frequency of the ionospheric F2-layer

In this work, active control method is proposed for controlling and synchronising seven-dimensional (7D) hyperchaotic systems. The seven-dimensional hyperchaotic system is considered for the implementation. Seven-dimensional hyperchaotic system is also investigated via time series, phase portraits and bifurcation diagrams. For understanding the impact of active controllers on global asymptotic stability of synchronisation and control errors, the Lyapunov function is used. Numerical analysis is done to reveal the effectiveness of applied active control method and the results are discussed.     

A Procedure for Rational Probe Liquids Selection to Determine Hansen Solubility Parameters

Hansen Solubility Parameters (HSP), viewed in the context of similarity whenever dispersion is focused, offer valuable insights into the surface characteristics of nanoparticles. However, existing methods for determining HSP via the sedimentation of nanoparticles require multiple probe liquids, resulting in time-consuming, costly experiments with potential health risks. To address this, we developed a two-step strategy that enables a systematic selection of liquids. The key element of the approach is to first identify the rough location of the Hansen sphere in the three-dimensional Hansen space using a well-chosen set of probe liquids of different polarities and chemical structures. Then, depending on the outcome of the first step, a particular choice of liquids is made for the final HSP determination. Taken together, the introduced procedure reduces the amount of required liquids for experiments from currently more than ten to a maximum of seven chosen based on a well-defined, coherent methodology. Validation was performed on carbon black, non-pigmentary nano-scale titania, silicon/carbon composites, and lanthanum cobaltite particles, i. e., relevant materials that are commonly utilized in fuel cells, batteries, cyclohexene oxidation, catalytic combustion, photocatalysis, and heterogeneous Fenton reactions. The study showcases the potential to save time, costs, and efficiently determine HSP values in a comparable manner.     

Determination of ivacaftor by liquid chromatography techniques in pharmaceutical formulation with interlaboratory comparison and characterization of five novel degradation products by high-performance liquid chromatography ion trap time-of-flight mass spectrometry

Cystic fibrosis is a life-threatening genetic disease that causes damage to the lungs. Ivacaftor, the first drug to target the underlying defect of the disease caused by specific mutations, improves outcomes and reduces hospitalizations. In this study, quantitative determination of ivacaftor was performed by liquid chromatography, while high-resolution mass spectrometric analyses were performed for qualitative determination. The validation studies of the developed methods were performed according to International Conference on Harmonisation Q2(R1) guideline. Ivacaftor was separated from its degradation product by using Phenomenex Kinetex C₁₈ (150 × 3 mm, 2.6 µm) column. The isocratic mobile phase for binary pump configuration was 0.1% (v/v) formic acid in water and 0.1% (v/v) formic acid in acetonitrile (27:63) (v/v), pH = 2.5; the flow rate of 0.25 mL/min was used in all methods. In the degradation studies, five degradation products were identified using high-performance liquid chromatography ion trap time-of-flight mass spectrometric analyses: three of them have never been reported up to date; whereas the other two were existing in the literature and they were having Chemical Abstracts Services registry numbers since they were synthesized before for various other purposes. Also, analysis of an in-lab prepared chemical equivalent of Kalydeco^® and interlaboratory comparison were performed.     

Liquid chromatographic determination of lumacaftor in the presence of ivacaftor and identification of five novel degradation products using high-performance liquid chromatography ion trap time-of-flight mass spectrometry

Lumacaftor is a transmembrane conductance regulator potentiator drug, prescribed for the treatment of cystic fibrosis in patients who are homozygous for the F508del mutation. Quantitation of lumacaftor besides its degradation products and ivacaftor was achieved on a fused-core silica particle column packed with pentafluorophenylpropyl stationary phase (Ascentis Express F5, 2.7 μm particle size 100 mm × 4.6 mm; Supelco) using gradient elution (A: 0.1% [v/v] formic acid in water, B: 0.1% [v/v] formic acid in acetonitrile [the mobile phase pH 2.5]). A constant flow rate at 1 mL/min was applied, and the detection was realized using a photodiode array detector set at 216 nm. The pseudo tablet formulation of the lumacaftor/ivacaftor fixed-dose combination preparation, namely, Orkambi®, was prepared in vitro and used for the analytical performance validation and method application studies. In addition, five novel degradation products, four of which even have no Chemical Abstracts Services registry number, were identified using high-resolution mass spectrometry instrument, and their possible mechanisms of formation were proposed. According to current literature, this paper can be regarded as the most comprehensive liquid chromatographic study on lumacaftor determination, among its counterparts.